1. Field of the Invention
The present invention relates to a spatial light modulator and a method of spatially modulating a radiation beam such as may be used in lithographic projection apparatus and device manufacturing methods.
2. Related Art
A lithographic apparatus is a machine that applies a desired pattern onto a target portion of a substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs), flat panel displays and other devices involving fine structures. In a conventional lithographic apparatus, a patterning means, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern corresponding to an individual layer of the IC (or other device), and this pattern can be imaged onto a target portion (e.g., comprising part of one or several dies) on a substrate (e.g., a silicon wafer or glass plate) that has a layer of radiation-sensitive material (resist). Instead of a mask, the patterning means may comprise an array of individually controllable elements that generate the circuit pattern on an impinging light beam.
In general, a single substrate will contain a network of adjacent target portions that are successively exposed. Lithographic apparatus include steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion in one pass, and scanners, in which each target portion is irradiated by scanning the pattern through the projection beam in a given direction (the “scanning”-direction), while synchronously scanning the substrate parallel or anti-parallel to this direction.
A significant problem in a lithographic apparatus using a programmable patterning means is uploading the data necessary to set the pixels of the programmable patterning means. To achieve throughputs and resolutions comparable with mask-based lithographic apparatus requires data transfer rates of 80 terabits per second or more. A typical programmable patterning means may have pixels of about 8 μm×8 μm and about 1000×4000 pixels. Multiple communication lines need to be operated in parallel to achieve the data rate required. Switching rates will be high and thus there is a large heat dissipation in a small device. Also, the necessary addressing circuitry is complex and difficult to fit in a small space.
Therefore, what is needed is a spatial light modulator to which pattern data can be uploaded without requiring complex addressing circuitry and with reduced heat dissipation.